Abstract The main objective of the present study was to develop and validate a new alternative modelling method to predict Bacillus tequilensis count in nutrient broth under iso-thermal and non-isothermal conditions. The bacterial growth data of Bacillus tequilensis was obtained experimentally in aerobically-kept nutrient broth medium and described with two-step and one-step modelling approaches by different primary models (the modified Gompertz, logistic, Baranyi and Huang models) under isothermal temperatures. Temperature-dependent kinetic parameter (maximum specific growth rate ‘µmax’) was described as a function of temperature via the Ratkowsky model integrated with each primary model. The Huang model based on the one-step modelling approach yielded the best fitting results (RMSE = 0.143 and adjusted-R2 = 0.977) for all isothermal conditions. Therefore, the Huang model was also used to check it’s prediction capability under non-isothermal conditions. The differential form of the Huang model provided satisfactorily statistical indexes (Bf = 1.07 and Af = 1.08) indicating reliably being able to use to describe the growth behaviour of Bacillus tequilensis in broth subjected to non-isothermal conditions.

Abstract Agaricus bisporus was washed with 1 g/L sodium chlorite (NaClO2) (SC) solution for 30, 60 and 120 s, packed with a non-perforated polyvinyl chloride (PVC) film and stored at 4 °C for 12 days. Washing the mushrooms with the SC solution and packaging with the PVC film slowed down the change in colour and firmness of the mushrooms, but treating the mushrooms with the SC solution longer than 60 s adversely affected the mushroom texture. After 12 days of storage, the weight loss of the mushrooms packed with the PVC film was less than 10% compared to the control. Headspace O2 concentration decreased while CO2 concentration increased throughout 12 days of storage and reached about 15% and 4%, respectively. Pseudomonas spp. counts for unwashed and unpacked mushrooms reached 10.30 log10 CFU/g after 12 days of storage while the mushrooms washed with the SC solution and packaged with the PVC film had Pseudomonas spp. counts as low as 6.62 log10 CFU/g. Treating the mushrooms with the SC solution for 60 s and packaging with the PVC film were found to be the most appropriate treatment to minimize the change on the postharvest quality of white button mushroom.

Abstract The colour of food is one of the most important factors affecting consumers’ purchasing decision. Although there are many colour spaces, the most widely used colour space in the food industry is L*a*b* colour space. Conventionally, the colour of foods is analysed with a colorimeter that measures small and non-representative areas of the food and the measurements usually vary depending on the point where the measurement is taken. This leads to the development of alternative colour analysis techniques. In this work, a simple and alternative method to measure the colour of foods known as “computer vision system” is presented and justified. With the aid of the computer vision system, foods that are homogenous and uniform in colour and shape could be classified with regard to their colours in a fast, inexpensive and simple way. This system could also be used to distinguish the defectives from the non-defectives. Quality parameters of meat and dairy products could be monitored without any physical contact, which causes contamination during sampling.

Abstract The colour assessment ability of the computer vision system is investigated and the data are compared with colour measurements taken by a conventional colorimeter. Linear and quadratic models are built to improve currently used methodology for the conversion of RGB colour units to L * a * b * colour space. For this purpose, two innovative ideas are proposed and tested. First, substantial amount of colour tones is generated to cover as many points in the colour space as possible. Secondly, the colour space is calibrated separately, whereas in previous research in the literature, the colour space is calibrated simultaneously. It is found that the RGB colour units to L * a * b * colour space transformation approach proposed in this study is more logical and more accurate, and the prediction performance of the quadratic model is superior over the linear model.